Irritable bowel syndrome (IBS) is a chronic, prevalent, often disabling, GI disorder for which there is no reliable and satisfactory medical option for its full range of symptoms (abdominal pain, bowel dysfunction). An accumulating body of evidence indicates that a specific psychosocial treatment called cognitive behavioral therapy (CBT) is associated with significant reductions in IBS symptoms and related difficulties. Despite its apparent efficacy, CBT's clinical effectiveness (i.e., its generalizability, feasibility, cost effectiveness) has not been adequately established due partly to its duration, cost, and limited accessibility. As the second generation of IBS treatments undergo development and validation, it has become increasingly clear that efficacy demonstration is a necessary but not sufficient condition of treatment viability. In a pilot study funded under NIDDK's R03 mechanism, we addressed these problems by developing a briefer, largely self administered version of CBT that requires only 4, I hr clinic visits. Our RCT data showed that a 10 session version of CBT can be translated into a 4 session version without compromising patient acceptability or short term efficacy. It is unclear whether treatment effects are maintained long term (out to 12 months), due to theoretical change mechanisms (vs. nonspecific factors common across different forms of therapy), are more pronounced among specific subgroups of patients, or, generalize to a large sample of Rome III diagnosed patients treated by different investigative sites. We seek to address these questions by conducting a larger, more definitive, multisite RCT that will recruit from 3 treatment sites 480 patients with moderate to severe IBS and assess their acute and long term response to brief (4 session) CBT, extended (10 session) CBT, or a credible attention placebo. We will use the first year to develop a clinical infrastructrue [sic] to ensure the success and integrity of the proposed trial. In the short term, a successful trial will lend empirical validation to a self administered version of CBT that retains the efficacy of standard CBT but is more transportable, accessible to patients outside of research protocols, and less costly to deliver. In the long term, we hope to show that a self guided behavioral treatment program is an effective and efficient treatment delivery system that can enhance the quality of patient care, improve clinical outcomes, and decrease the economic and personal costs of one of the most prevalent and intractable GI disorders. The primary goal of the proposed trial is to assess the short- and long-term efficacy of cognitive behavior therapy (CBT) for irritable bowel syndrome using two treatment delivery systems (self administered, therapist administered). Secondary aims seek to specify the conditions under which CBT may (or may not) achieve its effects (moderator questions), why and how these effects are achieved (mediator questions) and at what economic cost. Long term project goals are to develop an effective self-administered behavioral treatment program that can enhance the quality of patient care, improve clinical outcomes, and decrease the economic and personal costs of one of the most prevalent and intractable GI disorders.